System for electronically controlling and driving independently addressable semiconductor lasers

ABSTRACT

A computer adapted to convert images into raw data can provide the raw data to a control interface adapted to transmit the raw data with timing information to an electronic driver circuit. The electronic driver circuit can convert the raw data with the timing information provided by a control interface into regulated current signals provided to the semiconductor laser array at 300 dpi and higher. The semiconductor array can convert the current signals into light to illuminate an imaging member. The laser array can comprise vertical cavity surface emitting lasers providing imaging greater than 300 dpi. Each semiconductor laser can operate at 50 mW or greater.

TECHNICAL FIELD

Embodiments are related to controller and driver electronics forsemiconductors, including semiconductor lasers. More particularly,embodiments relate to a system for electronically controlling anddriving independently addressable semiconductor lasers.

BACKGROUND

Vertical cavity surface surface-emitting lasers (VCSELs) aresemiconductor-based lasers that emit light perpendicular to a substrate.If properly designed, technical uses of VCSEL arrays can include datacommunication systems, light detection and ranging (lidar) systems,printing systems, laser processing systems, zone heating or curing,illumination systems, 3d mapping systems, and facial recognition devices(e.g., smartphone face identification).

High power surface-emitting lasers typically require large aperturesbecause the light-emitting area of the device needs to be big enough tosupport the requisite high light output. For example, the typicalaperture of VCSELs capable of producing 50 mW of light output needs tobe about 18 μm in diameter or larger. The overall device size would belarger still because the device structure typically includes oxidationchannels and electrical contacts that extend beyond just the aperture.

One of the primary advantages of VCSELs is that if properly arrangedthey could be patterned into dense arrays with many hundreds orthousands of individual emitters operating as pixels. This would beimportant because some applications require high power surface-emittinglasers to be packed into tight-pitch arrays, where the linear pitch iscomparable to or smaller than the normal dimensions of the device. Forexample, in 1200 dpi printing applications, where each laser pixel inthe array would be used to address one dot on an image, the requiredlinear spacing between laser address lines would be about 21.2 μm. Thislinear pitch is tighter than the size of current semiconductor laserdevices capable of producing 50 mW of light output. Efficient or highintensity semiconductor lasers today often operate in wavelength regionsbetween 550 nm to 1000 nm. The very close spacing between lasers in sucharrays can make thermal crosstalk problematic, as heat from each lasercan affect the performance of nearby lasers. Also, the aggregateelectrical power drop from a large number of high power lasers operatingwithin a small region can lead to a high thermal load density that mustbe dissipated.

What is needed are independently-addressable VCSEL architectures thatcan produce high power at a resolution greater than 300 dpi and canaccommodate tight-pitch packing while overcoming thermally inducedshortcomings.

SUMMARY

The following summary is provided to facilitate an understanding of someof the innovative features unique to the disclosed embodiments and isnot intended to be a full description. A full appreciation of thevarious aspects of the embodiments disclosed herein can be gained bytaking the entire specification, claims, drawings, and abstract as awhole.

In accordance with the embodiments, a semiconductor laser (e.g., VCSEL)architecture is disclosed that can achieve 300 to at least 1200 DPIdigital addressability. The architecture can have features that includeimproved laser array designs, improved laser array geometries, and chiptiling. In printing applications, for example, VCSELs operating aspixels and deployed in an array format according to the presentembodiments can deliver up to and exceeding 50 milliwatts of laser powerwith aperture sizes that can enable high resolution (e.g., >300 dpi)resolution.

In accordance with the embodiments, a semiconductor laser array can beused as an individually addressable light source in, for example, theDALI (digital architecture for Lithographic Inks) printing processutilizing a dramatically reduced size and complexity for the mostsophisticated component in the printing system—the laser imager.

In accordance with the embodiments, large area, high power VCSEL arraysas presented herein also can be useful for various applications such asfacial recognition, laser sintering, contact-free thermochromicprinting, zone heating and curing, and lidar applications.

In accordance with the embodiments, a semiconductor laser array caninclude a mounting and cooling architecture that can maintain laseroperating temperatures and efficiency.

In accordance with a feature of the embodiments, a semiconductor laserarray can include direct die attachment to a submount with an integratedcooling channel.

In accordance with another feature of the embodiments, a semiconductorlaser array can include a transfer of an VCSEL epi layer onto a metalhost substrate.

In accordance with another feature of the embodiments another feature ofthe embodiments, a semiconductor laser array can implement image framephase delay addressing.

In accordance with another feature of the embodiments, a semiconductorlaser array can use a selfoc lens array.

In accordance with yet another feature of the embodiments, asemiconductor laser array can be integrated onto a submount.

In accordance with another feature of the embodiments, a semiconductorlaser array can incorporate a multi-row construction interposer design,including fan-in for ASIC placement tolerance.

In accordance with another feature of the embodiments, an interposerchip architecture can be provided that includes light pitch contact padson a semiconductor laser array fanning out from a narrow connection atthe semiconductor laser array to wider pitch pads on a PCB.

In accordance with another embodiment, a computer adapted to convertimages into raw data and can provide the raw data to a control interfaceadapted to transmit the raw data with timing information to driverelectronics.

In accordance with another embodiment, a current driver can convert theraw data with the timing information provided by a control interfaceinto regulated current signals provided to the semiconductor laser arrayvia the light pitch contact pads.

In accordance with another embodiment, the semiconductor array canconvert the current signals into light to illuminate an imaging member.

In accordance with another embodiment, the laser array can comprisevertical cavity surface emitting lasers providing imaging greater than300 dpi from multiple independently addressed apertures spaced up to 22micrometers apart.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying figures, in which like reference numerals refer toidentical or functionally-similar elements throughout the separate viewsand which are incorporated in and form a part of the specification,further illustrate the present invention and, together with the detaileddescription, serve to explain the principles of the embodiments.

FIG. 1 illustrates an architecture for an independently-addressable highpower laser array on 1200 dpi pitch, in accordance with the embodiments;

FIG. 2 illustrates an example block diagram of layout and dimensionsthat can satisfy achievement of high resolution lasing and imagingobjectives by staggering the arrangement of bond pads and trace lines,in accordance with the embodiments;

FIG. 3 illustrates an example block diagram of wire bonding connectionsfor individual lasers to their associated driver chips, in accordancewith the embodiments;

FIG. 4 illustrates a block diagram of an 11 inch-wide VCSEL imager for a1200 dpi printing system that can be comprised of multiple tiled laserarrays chips, in accordance with the embodiments;

FIG. 5 illustrates a block diagram of laser array chips placed in astaggered arrangement, in accordance with the embodiments;

FIG. 6 illustrates an optical micrograph for a portion of a 1200 dpilaser array utilizing an asymmetric laser aperture design, in accordancewith the embodiments;

FIG. 7 illustrates a chart of Light Output vs. Current Curves for adevice at different substrate temperatures showing peak output powers ofover 50 mW, in accordance with the embodiments;

FIG. 8 illustrates an optical micrograph for a portion of a 1200 dpilaser array utilizing a common anode multi-aperture pixel design, inaccordance with the embodiments;

FIG. 9 illustrates a chart of Light Output vs. Current Curves for onedual aperture common anode device at different substrate temperaturesshowing peak output powers of over 50 mW, in accordance with theembodiments;

FIG. 10A illustrates an optical micrograph for a portion of a 1200 dpilaser array utilizing a common anode triple-aperture pixel design, inaccordance with the embodiments;

FIG. 10B illustrates a closer view of the triple-aperture pixels of FIG.10(a) revealing 6 levels of staking in a process direction, inaccordance with the embodiments;

FIG. 11 illustrates an illustration of the backside view of a submountshowing how cooling fluid tubes can be attached to the submount and alsoshowing how integrated mounting holes can be formed therein forattaching optical elements, in accordance with the embodiments;

FIG. 12A to FIG. 12C illustrate front perspectives of lens arrays thatcan be used with semiconductor laser arrays;

FIG. 12D illustrates a three-point perspective diagram of imaging opticsincluding a 4-row se GRIN lens array that can be used with VCSEL arraysdescribed herein, in accordance with the embodiments;

FIG. 13 illustrates a graph for calculated Optical Throughout vs. SourceBeam Divergence for different laser spatial mode profiles, in accordancewith the embodiments;

FIG. 14A is a photograph of a four row GRIN-lens array (GLA) constructedfrom two modified 2-row SLAs, in accordance with the embodiments;

FIG. 14B illustrates an optical micrograph of the combined 2-row GLAs ofFIG. 14A, in accordance with the embodiments;

FIG. 15A illustrates a block diagram of staggered imaging system forlaser arrays, in accordance with the embodiments;

FIG. 15B illustrates an example of VCSEL scroll timing using a four-rowVCSEL laser array 170 with double apertures, in accordance with theembodiments;

FIG. 16 illustrates a feathered imaging system for laser arrays, inaccordance with the embodiments;

FIG. 17 illustrates an electrical thin film routing layout of aninterposer chip architecture that fans out tight-pitch contact pads on alaser array to wider-pitch contacts on a PCB or on a driver chip, inaccordance with the embodiments;

FIG. 18A illustrates a graph of Calculated Temperature vs. SubstrateThickness at different locations of a laser chip surface, in accordancewith the embodiments;

FIG. 18B illustrates a layout of a laser chip surface with a temperatureprofile shown across its surface, in accordance with the embodiments;

FIG. 19A to FIG. 19E illustrates process steps for transferring a VCSELarray epi to a metal host substrate, in accordance with the embodiments;

FIG. 20 , labeled as Prior Art, illustrates a diagram of components of aprinting system incorporating a laser array for inducing fountainsolution evaporation via laser patterning and associated printing steps,in accordance with the embodiments;

FIG. 21A illustrates a diagram of components of a completed VCSELarray-based imaging member, in accordance with the embodiments;

FIG. 21B illustrates a diagram of a side perspective of the completedVCSEL array-based imaging member presented in FIG. 21A;

FIG. 22 illustrates a block diagram of electronic modules operating aspart of a printing system, in accordance with the embodiments;

FIG. 23A to FIG. 23B illustrate block diagrams of programming statesduring printing when using a VCSELs for document processing, inaccordance with the embodiments;

FIG. 24 illustrates a block diagram representing functions that canoccur in primary modules of a printing system where VCSEL array usage isincorporated, in accordance with the embodiments; and

FIG. 25 illustrates another block diagram representing functions thatcan occur in primary modules of a printing system where VCSEL arrayusage is incorporated, in accordance with the embodiments.

DETAILED DESCRIPTION

The particular values and configurations discussed in these non-limitingexamples can be varied and are cited merely to illustrate one or moreembodiments and are not intended to limit the scope thereof.

Subject matter will now be described more fully hereinafter withreference to the accompanying drawings, which form a part hereof, andwhich show, by way of illustration, specific example embodiments.Subject matter may, however, be embodied in a variety of different formsand, therefore, covered or claimed subject matter is intended to beconstrued as not being limited to any example embodiments set forthherein; example embodiments are provided merely to be illustrative.Likewise, a reasonably broad scope for claimed or covered subject matteris intended. Among other things, for example, subject matter may beembodied as methods, devices, components, or systems. Accordingly,embodiments may, for example, take the form of hardware, software,firmware, or any combination thereof (other than software per se). Thefollowing detailed description is, therefore, not intended to beinterpreted in a limiting sense.

Throughout the specification and claims, terms may have nuanced meaningssuggested or implied in context beyond an explicitly stated meaning.Likewise, phrases such as “in one embodiment” or “in an exampleembodiment” and variations thereof as utilized herein do not necessarilyrefer to the same embodiment and the phrase “in another embodiment” or“in another example embodiment” and variations thereof as utilizedherein may or may not necessarily refer to a different embodiment. It isintended, for example, that claimed subject matter include combinationsof example embodiments in whole or in part.

In general, terminology may be understood, at least in part, from usagein context. For example, terms such as “and,” “or,” or “and/or” as usedherein may include a variety of meanings that may depend, at least inpart, upon the context in which such terms are used. Typically, “or” ifused to associate a list, such as A, B, or C, is intended to mean A, B,and C, here used in the inclusive sense, as well as A, B, or C, hereused in the exclusive sense. In addition, the term “one or more” as usedherein, depending at least in part upon context, may be used to describeany feature, structure, or characteristic in a singular sense or may beused to describe combinations of features, structures, orcharacteristics in a plural sense. Similarly, terms such as “a,” “an,”or “the”, again, may be understood to convey a singular usage or toconvey a plural usage, depending at least in part upon context. Inaddition, the term “based on” may be understood as not necessarilyintended to convey an exclusive set of factors and may, instead, allowfor existence of additional factors not necessarily expressly described,again, depending at least in part on context.

Although specific terms are used in the following description for thesake of clarity, these terms are intended to refer only to theparticular structure of the embodiments selected for illustration in thedrawings and are not intended to define or limit the scope of thedisclosure. In the drawings and the following description below, it isto be understood that like numeric designations refer to components oflike function.

Although embodiments are not limited in this regard, the terms“plurality” and “a plurality” as used herein may include, for example,“multiple” or “two or more”. The terms “plurality” or “a plurality” maybe used throughout the specification to describe two or more components,devices, elements, units, parameters, or the like. For example, “aplurality of stations” may include two or more stations. The terms“first,” “second,” and the like, herein do not denote any order,quantity, or importance, but rather can be used to distinguish oneelement from another. The terms “a” and “an” herein may not denote alimitation of quantity, but rather can denote the presence of at leastone of the referenced item.

The term “printing device”, “printing system”, or “digital printingsystem” as used herein can refer to a digital copier or printer,scanner, image printing machine, digital production press, documentprocessing system, image reproduction machine, bookmaking machine,facsimile machine, multi-function machine, or the like and can includeseveral marking engines, feed mechanism, scanning assembly as well asother print media processing units, such as paper feeders, finishers,and the like. The digital printing system can handle sheets, webs,marking materials, and the like. A digital printing system can placemarks on any surface, and the like and is any machine that can readmarks on input sheets; or any combination of such machines.

The term “pitch” as used herein can refer to the minimumcenter-to-center distance between interconnect lines. As a half pitchcan approximate the minimum linewidth, it can be used as an indicator ofan IC's integration level.

The term “semiconductor laser” as used herein can refer to surfaceemitting semiconductor lasers such as VCSELs (vertical cavity surfaceemitting lasers) or the like which can be fabricated on semiconductorsubstrate using semiconductor manufacturing techniques.

When properly designed, current state-of-the-art VCSELs(vertical-cavity-surface-emitting lasers) have the capability ofproducing enough light output power to be deployed in an array formatthat, if configured and packaged appropriately, could be used in highresolution evaporation of fountain solutions in high speed printingsystems. Such systems require each VCSEL in the array to produce tens ofmilliwatts of light output power as standalone devices when operatedalone and for the VCSEL array and its packaging to be designed so lasersretain that capability even when adjacent devices are simultaneouslyturned on. Features of embodiments provide, among other things, uniqueVCSEL array chip designs, that can result in high power small pitchindividually addressable lasers, ways to mount, cool, drive, and imagelarge numbers of VCSEL array chips so that wide width (>100 mm) printingcan be enabled with the chips, and an example of VCSEL arrays used forprinting in the DALI (digital architecture for Lithographic Inks)printing process.

To enable tight-pitch packing of independently-addressable high powersurface-emitting lasers on VCSEL array chips described herein. In someembodiments the VCSEL share a cathode and they are individuallyaddressable through individual address lines connecting individual VCSELanodes. In some embodiments a common anode addressing architecture canbe employed where each address line within the array can encompassmultiple electrically-connected apertures. Non-symmetric aperture shapescan also be employed that are elongated to fit within the pitch of theaddress lines. Additionally, the spacing of lasers in the processdirection can be tolerated by, for example, the Dali print process toincrease the total distance of lasers while still maintaining aneffective cross-process spacing that can be smaller than the size oflasers themselves.

“Pixel” can refer to a set of multiple VCSELs or 1 VCSEL. For example,in FIG. 6, 1 pixel comprises 1 laser. In FIG. 8, 1 pixel comprises 2lasers that are tied together. In FIG. 10, 1 pixel comprises a set of 3VCSELs.

The “aggregate linear pitch” as mentioned herein refers the crossprocess spacing between adjacent cross process direction lasersregardless of their position in the process direction. For example, inFIG. 8 , it is the cross process spacing between set B and set C, whichis 21.2 um. The “size of the laser” in FIG. 8 is the “width” of thecommon anode metal contact for laser set B.

Optimized thermal management of VCSEL array chips can be achieved, withtwo unique approaches (that can be used together): a) Direct die attachto mechanical blocks that incorporate means of cooling for example bycooling fluid channels or heat pipes, slots for driver chips, andmounting systems for optics and b) Ultra-thin laser epi transferred tothermally-conductive metal host substrates.

Allow stitching of VCSEL array chips is enabled so that the effective(stitched) laser array width meets the demand for today's productionprint width. The effective laser array contains means to focus the laserlight originating from the VCSELs, drive individual lasers, cool lasers,and extract evaporated fountain solution during DALI printingoperations.

VCSEL Array Chip Designs

Referring to FIG. 1 , illustrated is an architecture for anindependently-addressable high power laser array on 1200 dpi pitch, inaccordance with features of the embodiments. FIG. 1 illustrates anarrangement of a linear array 100 of VCSELs 110 with address trace lines115 having a 21.2 μm pitch. The electrical contact pads 120 must belarge enough to allow wire bonding, and the electrical trace lines 115must be wide enough to allow for low sheet resistance and negligiblevoltage drops when electrified with a signal during operation. In theembodiment shown, the semiconductor lasers 110 are arranged along tworows with one set of address lines 115 coming in from the top andanother set from the bottom. The two rows of lasers are offset relativeto each other to form an interdigitated linear array of light emitterson 21.2 μm pitch. The contact pads 120 on each side can also have astaggered arrangement so they can be large enough for wire bonding andstill fit within the available space between address lines. FIG. 1 showsa 21 mm long×2 mm wide chip which can contain 1000 lasers. Referring toFIG. 2 , illustrated further is an example layout 105 and dimensions forbond pads 120 and trace lines 115 that can further satisfy achievementof objectives illustrated in FIG. 1 .

Referring to FIG. 3 , illustrated is an example block diagram 130 ofwire bonding connections 133 for individual VCSELs 110 of each VCSELarray chip 100 to dedicated channels of their associated driver chips135, in accordance with the embodiments. The wire bonding connections133 to their respective driver chips 135 can have the identical pitch asthe laser pitch, or slightly varying pitch, for example smaller pitch.FIG. 3 illustrates how the individual laser chips 100 can be connectedto their respective driver chips 135 via wire bonding connection 133.

In an example implementation for printing, many laser array chips 100would be arranged side by side along a cross-process (or x) directionfor a document 101, as indicated by arrow 103 to form a wide imager 140.FIG. 4 illustrates a 14-chip arrangement forming an 11 inch-wide 1200dpi imager 140 to process images for documents 101 flowing in theprocess (or y) direction as indicated by arrow 102. The tiled laserarray chips 100 can also have a staggered arrangement 150 as illustratedin FIG. 5 to process images for documents 101 flowing in the processdirection 102 as shown, instead of a straight side-by-side arrangementas shown in FIG. 4 . In a staggered placement design, the portions ofthe print frame corresponding to the individual chips receiveappropriate timing delays, so the final image formed is stitchedcorrectly. Imperfections in alignment can also be accommodated byperforming calibrations to adjust the relative timing delays for eachlaser chip 100. In other embodiments, laser array chips can havededicated alignment structures to ensure correct alignment of twoneighboring laser array chips or correct alignment relative to thesupport structure.

In order to accommodate a large aperture size capable of deliveringlight outputs of up to 50 mW per laser, an asymmetric laser aperturedesign can be utilized, instead of a usual circular aperture. The shapeof the aperture can be “squeezed” along the direction of the array, soit fits within the available space of the tight pitch arrangement. Theaperture can be commensurately “elongated” in the direction of theaddress line to compensate for the squeezed dimension, so a sufficientlylarge light-emitting area still can be attained.

FIG. 6 illustrates an optical micrograph for a portion of a 1200 dpilaser array 160 utilizing an oblong 8×32 μm aperture shape for its VCSELlight emitters 110. The process direction 102 as shown by document icon101. The light emitters 110 can be arranged in 4 interdigitated rows 162with half of the addressing trace lines coming from the top side andhalf from the bottom side. The emitter aperture could be placed in adifferent angle so that the width in cross process direction iseffectively the same as the emitter pitch (e.g., 21.2 μm). For the 8×32μm aperture shape a 50.5 deg angle would accomplish that for example.FIG. 7 illustrates a graph of measured Light Output vs. Current curvesat different substrate temperatures for each VCSEL device, indicating apeak per-device light output power of over 50 mW.

Referring to FIG. 8 , illustrated is an optical micrograph for a portionof a 1200 dpi laser array 170 utilizing a common anode multi-aperturepixel design, in accordance with the embodiments. The process direction102 is shown by document icon 101. In this design, a common anodearchitecture is employed where each address line 115 within the arrayencompasses multiple electrically-connected apertures 175 to attain alarger effective overall aperture size. The double-aperture “pixel” 175in this embodiment can fit within a 1200 dpi pitch, yet each pixel(VCSEL 110) is capable of emitting more than 50 mW of light output, asillustrated in the graph 180 provided in FIG. 9 , where Light Output vs.Current is graphically depicted. The pixels can be arranged in 4interdigitated rows addressed from the top and bottom sides.

The multi-row interdigitated arrangement of pixels in FIGS. 1, 6, and 8can form an effectively tighter linear pitch in a “cross process”direction. In printing applications, an image can be formed row by rowas a media traverses across the laser array in the “process direction”,along the direction of the address lines. Each row of semiconductorlasers 110 can form a portion of the image. Since each row is spatiallyseparated from other rows, a time delay can be instituted between whenthe portion of an image from one row is formed relative to otherportions from other rows. In FIG. 8 , for example, pixels from the toprow must be placed adjacent to pixels on the bottom row, followed bypixels from the 2^(nd) from the top row and pixels just above the bottomrow. If these rows are labeled row A, B, C, and D from top to bottom andif the media is moving along the process direction from the bottom rowto the top, then the lasers on row A must be fired after those on row Dby a time delay equal to the distance between row A and D divided by themoving speed of the media. The image frames fed to rows A through D mustbe phase delayed to properly stitch together the image. The printresolution in the process direction can be most conveniently made thesame as that of the cross process direction if the separation betweenrows are multiples of the pixel spacing in the cross process direction.

Referring to FIG. 10A illustrated is an optical micrograph for a portionof a 1200 dpi laser array 190 utilizing a common anode triple-aperturepixel design, in accordance with the embodiments. FIG. 10B illustratesan even closer view of the triple-aperture pixel of FIG. 10A revealing 6levels of stacking in a process direction, in accordance with theembodiments. The process direction 102 for both Figures is once againshown with the flow of document icon 101. In this design, a common anodearchitecture can be employed where each address line 115 within thearray encompasses three electrically-connected apertures 195 to attain alarger effective overall aperture size for each pixel. In order toaccommodate the emitters 110, there can be a six level stacking schemein process direction implemented. The timing between the activation ofhorizontally adjacent pixels can be implemented in the driving software.With appropriate timing that accounts for the relative movement ofimaged member and laser; the semi-one dimensional positioning of laserscan result in a 1-dimensional printing line.

Mounting, Cooling, Driving, and Imaging VCSEL Array Chips

The tight spacing between lasers in such arrays makes thermal crosstalkproblematic, as heat from each laser affects the performance of nearbylasers. Also, the aggregate electrical power draw from a large number ofhigh power lasers operating within a small region leads to a highthermal load density that must be dissipated. Otherwise, the increasedtemperature will reduce the light output power and can damage thelasers.

These severe thermal management issues can be addressed by developing adirect die attached packaging approach, where the laser array chip isdirectly die-attached onto a 3D mechanical block, instead of aconventional planar submount. The mechanical block can incorporateembedded cooling fluid channels for flowing cooling fluids such aschilled water or ethylene glycol and functions as a cathode electricalcontact for the laser chip. The block can be thought of as a 3D submountwith a built-in heat sink. Our 3D submount also features integratedslots for driver chips or electrical interposers and mounting holes foroptics mounts. Alternatively, the submount could comprise a heat pipe.

Referring to FIG. 11 , illustrated is a photograph 230 of the backsideview of the mechanical block showing how cooling fluid tubes 233/235 canbe attached to the mechanical block 220 and also showing how integratedmounting holes can be formed therein for attaching optical elements, inaccordance with the embodiments. Cooling fluid channels 236 (dashedline) can be embedded inside the body of the mechanical block 220 andcan be made to flow coolants close to the heat source for efficient heatremoval. FIG. 11 also illustrates integrated mounting holes 237 that canbe provided for attaching optical elements used for imaging the laserbeams.

Focusing Optics

The light output from surface-emitting lasers diverges, so focusingoptics are typically needed to structure the light beams and formimages. Some commercial GRIN lens array marketed under the name SELFOClens arrays (SLA) can be configured and used for this purpose. SLAs arewell suited for this application because the optical elements can bearranged into a linear arrangement for imaging a set of laser elementsthat are also arranged in a linear array, such as the ones inapplications presented herein.

SLAs are devices that can be used to project a 1:1 image from a sourceto a substrate. These devices are typically quasi 1-dimensional and areused in scanning applications such as photocopiers, scanners, printers,and fax machines. Typically, SLAs are commercially available in 2-rowsof index graded optical elements bonded together in formats and they canbe used in some print applications such as LED print bars. Each opticalelement collects light from a source and projects it on to a substrate.Images from all the optical elements superimpose in order to form theprojection of the source onto the substrate. SLAs are attractive becausetheir size can be relatively large so that they become usable forprinting applications which typically require wide print width.Commercial SLAs are approximately 12 inch wide. In accordance with thepresent embodiments, should significantly wider print widths berequired, several SLAs could be stitched along the cross-processdirection or longer custom SLAs could be produced, or complete VCSELprint bars could be staggered for use in a wide Dali print process.

Referring to FIG. 12A, a diagram of a two-row SLA is illustrated. Oneproblem with SLAs is that incident light is either captured by theoptical 240 elements or are absorbed by a bonding agent 241 used tosecure the optical elements 240. Ideally, a bonding agent would betransparent to the laser light, in particular near infrared light.Approximately 26% of incident light can be absorbed by the bonding agent241. Therefore, the optical element fill factor is: 2pi( )/(4+2*sqrt(5))=74%. Many imaging application require little power, so losing 26%of the light is not an issue. Applications, such as thermal processes(e.g., patterned sintering or evaporation), however, require highoptical power. For application that require high power, this can createtwo issues: the SLA can heat up, which then requires a system design andoptical design which can tolerate the heat, and energy by the bondingagent 241 is wasted thus requiring more power from the source element toachieve a desired thermal response. An overall light utilization of morethan 50% can be considered as well usable for many applications,including thermal processes.

Referring to FIG. 12B, a solution that can overcome the absorptionproblem with currently available SLAs is to provide an SLA design wherethe bonding agent can be replaced by a transparent polymer 242. Usingthis type of bonding agent can allow diffused light to pass through theSLA and be delivered to the substrate. Thermal processes are oftenthreshold dependent. An entire area can be heated, but the desiredeffect will only be seen where enough energy is present to initiate thethermal process. Diffused light can act as a pre-heat or post-heat toprovide thermal offset to the area to be imaged. This can allow somefraction of the 26% lost light to be used in the thermal process and canhelp keep the SLA cool. Scattering elements 243 can also be incorporatedin the bonding agent to accomplish light diffusion. Referring to FIG.12C, a geometry is shown that can accomplish more diffused light whencompared to the geometry illustrated in FIG. 12B, which can provide morefocused light.

Referring to FIG. 12D, illustrated is a three-point perspective diagram243 of imaging optics including a 4-row GRIN lens array that can be usedwith VCSEL arrays described herein, in accordance with the embodiments.FIG. 12D illustrates an example implementation utilizing a 4-rowGRIN-lens array. The light path 244 from each laser 110 can traversesseveral lens elements 245 and converge on an image plane 247. FIG. 13illustrates a graph 249 of the calculated Transmission efficiency vs.beam Divergence for different laser spatial mode profiles. The opticalthroughput can be limited by the imperfect fill factor of the GRIN lensarray, as light that lands on the material at the gaps between thecylindrical optical elements is lost. Diverging light that is notcaptured by the lens array is also lost, so it is beneficial to use theenough rows if lenses to capture ideally all the light emanating fromthe VCSEL array.

A larger number of lens rows can be constructed from commerciallyavailable 2-row SLAs by removing the cladding from one side of the SLA,polishing away the cladding residues, and pressing two modified SLAstogether. Referring to FIG. 14A, illustrated is a photograph 250 of afour row SLA constructed from two modified 2-row SLAs, in accordancewith the embodiments. Referring to FIG. 14B, illustrated is an opticalmicrograph 255 of the combined 2-row SLAs 250 depicted in FIG. 14A.

Alternative Focusing Optics

In many cases the desired print width makes a classical imaging systemtoo large. Instead of using SLAs to focus an image 110 of individualVCSEL lasers of a laser array 100 on a blanket cylinder 266, it also canbe possible to use different optical elements such as classical focusinglenses 263. These types of lenses or lens combinations create invertedimages of an object. Referring to FIG. 15A, illustrated is a blockdiagram of a staggered imaging system 260 for focusing output from VCSELlaser arrays 100, in accordance with the embodiments. It can benecessary to stagger individual imaging systems 100 in a sawtoothpattern as illustrated in FIG. 15A. Each row in the staggered system isactivated with an appropriate timing delay 265 (e.g., t₀, t₀+Δt, to+Δ2t) so the aggregate exposures made on the moving imaging member 266are properly stitched to form the intended image.

Referring to FIG. 15B, an example of VCSEL scroll timing using afour-row VCSEL laser array 170 with double apertures (see FIG. 8 ) isshown where a document 101 is being processed in the process direction102 at 1 m/sec, with 55 μm row spacing (center to center) between VCSELrows. As the document 101 is being processed in the processing direction102, pixels in each row will illuminate at different times in accordancewith a reference image in order to accommodate distance between pixelsbased on their row assignment. Pixels in row 1 is shown illuminatingwith timing equal to 0.00 microseconds, while pixels in row 2 are shownto illuminate at 55.00 microseconds, with row 3 at 110.00 microseconds,and row 4 at 165.00 microseconds. Thus, accounting for delays asdescribed can enable image stitching accuracy during documentprocessing.

Referring to FIG. 16 , illustrated is a feathered imaging system 270 forfocusing output from laser arrays 100, in accordance with theembodiments. Focusing of output can be achieved by interleaving theindividual laser arrays 271/272 into an at least partially sharedimaging path 275 onto an imaging member 266 (e.g., drum) as illustratedin FIG. 16 , by combining beams using a beam combiner such polarizationoptics 274 or dichroic mirrors or both. A combination of polarizationand spectral beam combiners, as well as a cascade of beam combinerscould be used to combine images.

Referring to FIG. 17 , illustrated is a block diagram of an interposerchip architecture 300 that fans out tight-pitch contact pads 315 on alaser array 100 to wider-pitch pads 325 on a PCB or on a driver chip, inaccordance with the embodiments. For high resolution printingapplications such as 1200 dpi or higher, the required laser array pitchis very tight compared to the typical dimensions of pads and pad spacingin state-of-the-art PCBs. In some implementations, an interposer chip300 that fans out electrical contacts 315 from the laser chip 100 tomatch a wider-pitched set of contact pads on a PCB or a driver chip canbe used. FIG. 17 illustrates an example of an embodiment where aninterposer is employed to fan out the contact pads 315 on 42 μm pitch to100 μm pitch pads 325. This interposer design can be used on both sidesof a laser chip to address an interdigitated array of lasers 100 on 1200dpi pitch.

There is an alternative interposer design that can fan the contact pitchin, rather than out. In such designs, the VCSEL array pads can be mappedto corresponding tighter-pitch pads, say, on the output of a driver chip(ASIC). The fan-in arrangement allows the driver chip to be made smallerthan the laser array chip, thus providing placement tolerance whenaligning and tiling driver chips for addressing tiled laser array chips100 like those in FIG. 3 .

Substrate Thinning

In certain applications, the ability to directly attach the laser arraychip 210 onto a large highly thermally conductive block 220 is essentialfor preventing thermal overload, because a traditional 2D planarsubmount would add unacceptable thermal resistance between the laserchip 210 and a heat sink. In the presented cooling design as describedwith respect to FIG. 11 , highly concentrated heat generated within thesmall area of the laser chip 210 can quickly enter the copper block 220,spread across the large area of the block 220, and can be dissipated outof the system via fast-flowing coolant fluids running through tubes233/235.

The semiconductor laser substrate is typically highly thermallyresistive compared to a metal block, so the substrate can present asignificant bottleneck to thermal flow from heat generated at thelasers. Thermal modeling indicates that thinning the substrate from aconventional 150 μm thick layer to 40 μm can reduce the temperature atthe laser by 12° C. during operation, assuming a coolant flow rate of 4liters per minute. This can translate into a light output powerimprovement of about 10%. The temperature at the laser can be reducedfurther with the use of thinner substrates down to a substrate thicknessof 20 μm.

FIG. 18A illustrates a graph 340 of Calculated Temperature vs. SubstrateThickness at different location of a laser ship surface, in accordancewith the embodiments. The calculation assumes the laser array geometryshown in FIG. 1 , the 3D submount design shown in FIG. 3 , an ethyleneglycol coolant temperature of −10° C., and a coolant flow rate of 4L/min. FIG. 18B illustrates a diagram 345 if the temperature profileacross the laser chip surface corresponding to the plot points shown inFIG. 18A. The device under test was an off-state device and thetemperature at that location was calculated when all lasers in the arrayare turned on to full power. This temperature is a measure of thermalcrosstalk and of the effect of neighboring lasers on the performance ofthe device under test.

A 20 μm-thick layer is in the order of the thickness of the VCSELepitaxial layers, so the substrate thinning task is tantamount toremoving the epi material from its native substrate and transferring itto a host metal substrate. FIGS. 19A to 19E illustrate a process forachieving this task. The first step comprises mounting the laser chip355 including substrate 344, backside 356 facing upward, and withmounting wax 358 onto a planar handle wafer 350, such as glass orsilicon, as illustrated in FIG. 19A. Then as shown in FIG. 19B, thebackside 356 is chemical-mechanically polished so only 20 μm ofmaterials remains. For GaAs substrates, the polishing step can beperformed using sodium hypochlorite in conjunction with a rotating softpad. Thickness control can be achieved using a mechanical stop designedinto part of the substrate holder. Alternatively, the GaAs substrate canbe selectively removed by employing an etch stop layer in the epilayerstack in combination with a chemical etchant that etches GaAs fasterthan the etch stop layer. For example, a thin layer of AlGaAs can beused as an etch stop against NH₄OH/H₂O₂. Another example utilizes GaInPas an etch stop against HNO₃/H₂O₂. The handle wafer 350 can then beremoved from a polishing jig and placed into a thin film evaporator. Inthe evaporator, an n-type ohmic contact metal 357 such as AuGe can beblanket deposited on the polished backside 356 of now thinned substrate344, as shown in FIG. 19C. Next, as shown in FIG. 19D, the backsidemetal film can be used as an electroplating seed for electroforming of alayer of electroplated metal 359 that replaces the removed substrate.The electroplated metal 359 can be, for example, a 50 μm-thick layer ofcopper. Then, as illustrated in FIG. 19E, the handle wafer 350 can beremoved by dissolving the mounting wax 358 in a solvent such as acetone,which will enable the handle wafer 350 to be removed from the modifiedlaser chip 355. This step can leave the electroplated metal 359 holdingthe transferred laser epi 333. The host substrate 356 and thetransferred laser array 333 can then be annealed to complete the n-sideohmic contact interface. The completed structure can then be dieattached to a mechanical block 220 as previously described.

VCSEL Array Printing Application Example

Not meant as a limitation for application herein disclosed embodiments,as mentioned hereinbefore, the use of VCSEL arrays as an individuallyaddressable light source in, for example, digital architecture forlithographic inks (DALI) printing systems. DALI print processing has theadvantage of a dramatically reduced size, cost, and complexity of themost sophisticated component—the laser imager.

FIG. 20 illustrates a schematic diagram of a prior art digital printingsystem 370 that includes an imaging member 266. The digital printingsystem 370 can be implemented as a system for variable lithography. Theimaging member 266 in the example depicted in FIG. 20 may be a drum, aplate or a belt, or another now known or later developed configuration.

The imaging member 266 can be used to apply an ink image to an imagereceiving media substrate 114 at a transfer nip 112. The transfer nip112 can be formed by an impression roller 118, as part of an imagetransfer mechanism 160, exerting pressure in the direction of theimaging member 266. The image receiving media substrate 114 should notbe considered to be limited to any particular composition such as, forexample, paper, plastic, or composite sheet film. The digital printingsystem 370 may be used for producing images on a wide variety of imagereceiving media substrates.

The imaging member 266 can include a reimageable surface layer formedover a structural mounting layer that may be, for example, a cylindricalcore, or one or more structural layers over a cylindrical core.

The digital printing system 370 can include a fountain solution system122 that involves a series of rollers, which may be considered asdampening rollers or a dampening unit, for uniformly wetting thereimageable surface of the imaging member 266 with dampening fluid. Apurpose of the fountain solution system 122 is to deliver a layer ofdampening fluid, generally having a uniform and controlled thickness, tothe reimageable surface of the imaging member 266.

As indicated above, it is known that a dampening fluid such as fountainsolution may comprise mainly water optionally with small amounts ofisopropyl alcohol or ethanol added to reduce surface tension as well asto lower evaporation energy necessary to support subsequent laserpatterning, as will be described in greater detail below. Small amountsof certain surfactants may be added to the fountain solution as well.Alternatively, other suitable dampening fluids may be used to enhancethe performance of ink based digital lithography systems.

Once the dampening fluid is metered onto the reimageable surface of theimaging member 266, a thickness of the dampening fluid may be measuredusing a sensor 125 that may provide feedback to control the metering ofthe dampening fluid onto the reimageable surface of the imaging member266 by the fountain solution system 122.

After a precise and uniform amount of dampening fluid is provided by thefountain solution system 122 on the reimageable surface of the imagingmember 266, an optical patterning subsystem 130 may be used toselectively form a latent image in the uniform dampening fluid layer byimage-wise patterning the dampening fluid layer using, for example,laser energy. Typically, the dampening fluid may not absorb the opticalenergy (IR or visible) efficiently. The optical patterning subsystem 130can be implemented as or may include a light source 131 (e.g., avertical cavity surface emitting (VCSEL) array, a light emitting diode(LED) array, a laser light source that emits the pixilated light beam asa pixelated line laser beam, or a modulated laser line source).

The reimageable surface of the imaging member 266 should ideally absorbmost of the laser energy (visible or invisible such as IR) emitted fromthe optical patterning subsystem 130 close to the surface to minimizeenergy wasted in heating the dampening fluid and to minimize lateralspreading of heat in order to maintain a high spatial resolutioncapability. Alternatively, an appropriate radiation sensitive componentmay be added to the dampening fluid to aid in the absorption of theincident radiant laser energy. While the optical patterning subsystem130 is described above as being or including a light source such as alaser emitter, it should be understood that a variety of differentsystems may be used to deliver the optical energy to pattern thedampening fluid.

The mechanics at work in the patterning process undertaken by theoptical patterning subsystem 130 are known to those in the art. Briefly,the application of optical patterning energy from the optical patterningsubsystem 130 can result in selective removal of portions of the layerof dampening fluid.

Following patterning of the dampening fluid layer by the opticalpatterning subsystem 130, the patterned layer over the reimageablesurface of the imaging member 266 can be presented to an inker subsystem145. The inker subsystem 145 can be used to apply a uniform layer of inkover the layer of dampening fluid and the reimageable surface layer ofthe imaging member 266. The inker unit 145 can further include heatedink baths whose temperatures can be regulated by a temperature controlmodule (not shown in FIG. 20 ). The inker subsystem 145 can use ananilox roller to meter an offset lithographic ink onto one or more inkforming rollers that can be in contact with the reimageable surfacelayer of the imaging member 266. Separately, the inker subsystem 145 caninclude other traditional elements such as a series of metering rollersto provide a precise feed rate of ink to the reimageable surface. Theinker subsystem 145 can deposit the ink to the pockets representing theimaged portions of the reimageable surface, while ink on the unformattedportions of the dampening fluid will not adhere to those portions.

The cohesiveness and viscosity of the ink residing in the reimageablelayer of the imaging member 110 can be modified by a number ofmechanisms. One such mechanism, for example, can involve the use of arheology (complex viscoelastic modulus) control subsystem 155. Therheology control system 155 can form a partial crosslinking core of theink on the reimageable surface to, for example, increase ink cohesivestrength relative to the reimageable surface layer. Curing mechanismsmay include optical or photo curing, heat curing, drying, or variousforms of chemical curing. Cooling may be used to modify rheology as wellvia multiple physical cooling mechanisms, as well as via chemicalcooling.

The ink can be then transferred from the reimageable surface of theimaging member 266 to a substrate of image receiving medium 114 using atransfer subsystem 160. The transfer occurs as the substrate 114 ispassed through a nip 112 between the imaging member 266 and animpression roller 118 such that the ink within the voids of thereimageable surface of the imaging member 266 is brought into physicalcontact with the substrate 114. With the adhesion of the ink having beenmodified by the rheology control system 155, modified adhesion of theink causes the ink to adhere to the substrate 114 and to separate fromthe reimageable surface of the imaging member 266. Careful control ofthe temperature and pressure conditions at the transfer nip 112 canallow transfer efficiencies for the ink from the reimageable surface ofthe imaging member 266 to the substrate 114 to exceed 95%. While it ispossible that some dampening fluid may also wet substrate 114, thevolume of such a dampening fluid will be minimal and will rapidlyevaporate or be absorbed by the substrate 114.

In certain offset lithographic systems, it should be recognized that anoffset roller (not shown in FIG. 20 ) can first receive the ink imagepattern and then transfer the ink image pattern to a substrate accordingto a known indirect transfer method. Following the transfer of themajority of the ink to the substrate 114, any residual ink and/orresidual dampening fluid must be removed from the reimageable surface ofthe imaging member 266, preferably without scraping or wearing thatsurface. An air knife may be employed to remove residual dampeningfluid. It is anticipated, however, that some amount of ink residue mayremain. Removal of such remaining ink residue may be accomplishedthrough use of some form of cleaning subsystem 172. The cleaningsubsystem 172 can comprise at least a first cleaning member such as asticky or tacky member in physical contact with the reimageable surfaceof the imaging member 266, the sticky or tacky member removing residualink and any remaining small amounts of surfactant compounds from thedampening fluid of the reimageable surface of the imaging member 266.The sticky or tacky member can then be brought into contact with asmooth roller to which residual ink may be transferred from the stickyor tacky member, the ink being subsequently stripped from the smoothroller by, for example, and a doctor blade.

Other mechanisms by which cleaning of the reimageable surface of theimaging member 266 can be facilitated. Regardless of the cleaningmechanism, however, cleaning of the residual ink and dampening fluidfrom the reimageable surface of the imaging member 266 can be essentialto preventing so-called ‘ghosting’. Once cleaned, the reimageablesurface of the imaging member 266 can be again presented to the fountainsolution system 122 by which a fresh layer of dampening fluid can besupplied to the reimageable surface of the imaging member 266, and theprocess can be repeated.

In the prior art digital printing system 370 shown in FIG. 20 , ablanket 113 (i.e., an ‘imaging cylinder blanket’ or ‘imaging blanket’)is shown. The imaging member 266 in the form of a printing plate cansurround the cylindrically shaped blanket 113. The blanket 113 with theimaging member 266 in the form of a printing plate shown in the FIG. 20example can rotate in the direction indicated by curved arrow 117.

The ink must be compatible with materials that it comes into contactwith, including the imaging member 266, fountain solution applied byfountain solution system 122, and other cured or non-cured inks. The inkshould also meet all functional requirements of the sub-systems,including wetting and transfer properties. Transfer of the imaged inksis challenging, as the ink must at once wet the blanket materialhomogeneously (e.g., imaging member 266), and transfer from the blanket113 to the substrate (112, 114, and 118). Transfer of the image layermust be very efficient, at least as high as 90%, as the cleaningsub-station can only eliminate small amounts of residual ink. Any inkremaining on the blanket after cleaning would result in an unacceptableghost image appearing in subsequent prints. Not surprisingly, inkrheology plays a key role in the transfer characteristics of an ink.

DALI print systems involve the use of DALI print process high powerlasers and the ability to modulate them in a pixel-by-pixel fashion toproduce latent fountain solution images that can be used to ink aprinting blanket. A DALI system can enable the digital printing of highviscosity inks with high resolution. Such a high quality printingprocess can combine the inherent advantages of high pigment loading, lowsolvent content, inexpensive inks with the capability of printing withthese inks in a digital fully customizable manner for each pixel in eachprint.

In the DALI printing process, a continuous thin layer (e.g., tens ofnanometers) of fountain solution, which can be deposited on the surfaceof the printing blanket, rejects the transfer of ink to the blanket 113(in particular imaging member 266). A high-power laser can be used toheat the surface region of the optically absorbing blanket and therebyevaporate the fountain solution in an image-wise pattern. The lasermust, however, heat the blanket sufficiently to supply the latent heatof evaporation as well as the sensible heat to raise the fluid to itsevaporation temperature (e.g., —175C). The evaporated areas can be theninked, and the ink can be transferred to a receiving medium.

Although existing DALI printing systems can enable the digital printingof high viscosity inks with a high resolution, the current DALI printingprocess can be relatively expensive due to the cost of high-power lasersand their modulation devices. Solutions such as those described withrespect to the embodiments described herein are thus needed to reducecosts significantly for DALI printing systems.

A design drawing of a completed VCSEL array-based imaging member 380 isdepicted in the perspectives presented in FIGS. 21A and 21B. A macrointerposer PCB 225 is shown attached to the VCSEL cooling block 220. AVCSEL array 210 is shown attached to the VCSEL cooling block 220 and aGRIN lens array 240 is shown aligned with the VCSEL array 210 andpositioned opposite the VCSEL cooling block 220. In addition to thedescribed elements, FIGS. 21A/21B can also include a vapor extractionunit 388 that is mounted to a vapor extraction mount 387 and placedclose to the focus area (output) of the GRIN lens array 240. In someembodiments the vapor extraction unit 388 can include a vacuum blade 389or a physical blade or both. The vapor extraction unit 388 can extractfountain solution vapor generated by selective laser heating during theprocess of digitally structuring the fountain solution. FIG. 21B shows agenerally location for wire bonds 382 and a VCSEL interposers 381/384,as well as a focal plane 360 which would typically be adjusted to belocated on the blanket cylinder 375. FIG. 21A show a location wherevapor extraction adjustment 383 can occur. Furthermore, as depicted inFIG. 11 a cooling fluid tube 233 which can provide coolant to the VCSELcooling block 220 may be attached to the block.

Referring to FIG. 22 , illustrated is a block diagram 400 of electronicmodules operating as part of a printing system, in accordance with theembodiments. Electronic modules as shown can provide system functions ofthe application specific integrated circuit (ASIC) driver chips 135mentioned with respect to FIG. 3 and the discussion thereafter.Electronic modules as shown can together enable a system for controllingand driving independently addressable semiconductor lasers. A computer405 can be provided that converts images into raw data and provides itto a control interface 410. The control interface 410 can then transmitraw data and timing to driver electronics 415. A current driver 415 canconvert raw data with timing information provided by the controlinterface 410 into regulated current signals. Then, a VCSEL array 420can convert the current signals into light used to illuminate an imagingmember 266 (see FIG. 15A).

Referring to FIGS. 23A-B, illustrated is a block diagram 450, which isjust one example of the functional states that could be implemented inthe control interface circuit. The control interface circuit can ingeststreams of image data for each row of VCSEL devices from the computerand convert them into timing signals and properly timed raw data for thecurrent driver circuit to power the VCSEL devices in a manner to producethe desired print output. The interface circuit requires streams ofimage data, as well as system information including, but not limited to,print media speed, print media acceleration, deceleration, and device todevice variation in VCSEL power. In the idle state 460 the controlinterface is typically waiting for image data from the computer. In thePrint Setup State 470 the control interface circuit receives and bufferspre-formatted image data stream from the computer for each VCSEL row inpreparation to produce the desired print output. In the Print Linesstate 451-454, data for each row of a 4 row VCSEL array is responsive tosubframe delay 458 data to produce a properly stitched and timed imageon the drum. Each print line can process data and timing informationusing display line, send next line and memory access modules based onimage processing data received from a print setup 470 module. Afterdocument processing, the system can revert back 459 to an idle state 460an await additional/new processing requirements.

Referring to FIG. 24 , a block diagram 500 is illustrated, whichrepresents functions that can occur in primary modules of a printingsystem where VCSEL array usage is incorporated, in accordance with theembodiments. As shown in Block 503, an image can be converted into 4data streams (A,B,C, and D) to accommodate each of the 4 rows of theVCSEL array. Concurrently with this, timing information can be convertedto clock pulse values and sent to FPGA memory where current set pointare set, as depicted at Block 505. Image data can be buffered into FPGAmemory using DMA function as illustrated at Block 510, while timinginformation can be retrieved from FPGA memory and stored in FPGAregisters as indicated at Block 513. Then, as shown at Block 515,electrical current setpoint information can be stored in dot correctionregisters at the print module in preparation for further documentprocessing/rendering using VCSELs.

Referring to FIG. 25 , another block diagram 550 is illustrated, whichrepresents functions that can occur in electronic modules of a printingsystem where VCSEL array usage is incorporated, in accordance with theembodiments. As described at block 555, print start and stop operationcan be initiated at the computer after steps described herein withrespect to FIG. 24 . As illustrated at Block 560, image data can beretrieved from FPGA memory for each print line and can be formatted andshifted out of the FPGA to the module. Concurrently, as shown in Block563, control (CNTRL) signals can be raised and lowered for each group(ABCD) based on timing values stored in registers. Then, as indicated atBlock 565, current outputs can be activated according to values in GrayScale registers at the start of the cycle for each print line.Furthermore, while currents are being output, next line data is beingshifted int o Gray Scale Registers.

In summary, structures and methods are disclosed herein for realizingtight-pitch independently-addressable high power surface-emitting laserarrays. Also described herein are associated components and methods toenable use of such laser arrays in printing applications.

It will be appreciated that variations of the above-disclosed and otherfeatures and functions, or alternatives thereof, may be desirablycombined into many other different systems or applications. It will alsobe appreciated that various presently unforeseen or unanticipatedalternatives, modifications, variations, or improvements therein may besubsequently made by those skilled in the art which are also intended tobe encompassed by the following claims.

1. A system for electronically controlling and driving a plurality ofindependently addressable semiconductor lasers, comprising: surfaceemitting lasers arranged in a linear laser array comprised of at least100 laser devices on a common substrate chip and a dedicated channelassociated with an address trace line and connection point for each ofthe surface emitting lasers in the linear laser array; an electroniccurrent driver circuit capable of individually controlling the lightoutput of each surface emitting laser among the surface emitting lasersby providing electric drive current to the each surface emitting laserthrough the connection point and address trace line associated with theeach surface emitting laser; a control interface circuit which receivesa stream of digital image data from a computer and converts the digitalimage data into raw data, which the electronic current driver circuituses to apply a current to the each surface emitting laser, wherein thecontrol interface circuit and the electronic current driver circuit areimplemented on an ASIC, and wherein the control interface circuit andthe electronic current driver circuit are paired with a substrate chipcontaining the linear laser array; and an interposer chip thatcommunicates with the ASIC and the substrate chip containing the linearlaser array, wherein the interposer has an array of input electricalconnection points and an array of output electrical connection points,wherein each input connection point is electrically connected to exactlyone output connection point, wherein the array of input connectionpoints is in close proximity to the ASIC and the spacing betweeninterposer input connection points is identical to the spacing of theASIC output connection points for the laser current driver circuit, andwherein the array of output connection points on the interposer chip isin close proximity to the substrate chip containing the linear laserarray and the spacing between interposer output connection points isidentical to the spacing of the device connection points on thesubstrate chip containing the linear laser array.
 2. The system of claim1, wherein the surface emitting lasers are configured to produce alinear image on a surface.
 3. The system of claim 1, wherein the surfaceemitting lasers, when actuated properly in time, are configured toproduce a linear image on a surface in motion.
 4. The system of claim 1,wherein the semiconductor lasers are vertical cavity surface emittinglasers configured in an array designed to generate a linear imageresolution of at least 300 dpi.
 5. The system of claim 1, wherein theelectronic current driver circuit is configured to produce at least 50mW from the each of the surface emitting lasers.
 6. The system of claim1, wherein the semiconductor lasers are vertical cavity surface emittinglasers configured in an array.
 7. The system of claim 1, wherein thesurface emitting lasers are operable to produce a linear image on asurface in motion.
 8. The system of claim 7, wherein the controlinterface circuit receives in addition to the stream of digital imagedata, information comprising data indicative of print media speed, printmedia acceleration, print media deceleration and device-to-devicevariation in surface emitting laser power.
 9. The system of claim 1,wherein the ASIC current driver circuit output connection pointscomprise an array with identical spacing to match the device spacing ofthe substrate chip containing the linear laser array.
 10. The system ofclaim 8, wherein.
 11. The system of claim 1, further comprising acomputer which generates the digital data stream from an external inputincluding a digital file of the image to be printed, the speed at whichthe print media is moving through at least one of: the system, aphysical location of the each surface emitting laser in the system, aperformance characteristics of the each surface emitting laser in thesystem.
 12. A system for electronically controlling and driving aplurality of independently addressable semiconductor lasers, comprising:vertical cavity surface emitting lasers arranged in a linear laser arraycomprised of at least 100 laser devices on a common substrate chip and adedicated channel associated with an address trace line and connectionpoint for each of the vertical cavity surface emitting lasers, whereinthe vertical cavity surface emitting lasers are configured in the arrayto generate a linear image resolution of at least 300 dpi; an electroniccurrent driver circuit for individually controlling the light output ofeach vertical cavity surface emitting laser by providing electric drivecurrent to each vertical cavity surface emitting laser through theconnection point and address trace line associated with the eachvertical cavity surface emitting laser, wherein the vertical cavitysurface emitting lasers are operable to produce a linear image on asurface; and a control interface circuit which receives a stream ofdigital image data from a computer and converts the digital image datainto raw data which the electronic current driver circuit uses to applyan appropriate current to each vertical cavity surface emitting laser atan appropriate time, wherein the control interface circuit and theelectronic current driver circuit are implemented on an ASIC, andwherein the control interface circuit and the electronic current drivercircuit are paired with a substrate chip containing the laser array; andan interposer chip that communicates with the ASIC and the substratechip containing the laser array, wherein the interposer has an array ofinput electrical connection points and an array of output electricalconnection points, wherein each input connection point is electricallyconnected to exactly one output connection point, wherein the array ofinput connection points is in close proximity to the ASIC and thespacing between interposer input connection points is identical to thespacing of the ASIC output connection points for the laser currentdriver circuit, and wherein the array of output connection points on theinterposer chip is in close proximity to the substrate chip containingthe linear laser array and the spacing between interposer outputconnection points is identical to the spacing of the device connectionpoints on the substrate chip containing the linear laser array.
 13. Thesystem of claim 12, wherein the vertical cavity surface emitting lasers,when actuated properly in time, are configured to produce a linear imageon a surface in motion.
 14. The system of claim 12, wherein theelectronic current driver circuit is configured to produce at least 50mW from each of the vertical cavity surface emitting lasers.
 15. Thesystem of claim 12, wherein the surface emitting lasers are operable toproduce a linear image on a surface in motion.
 16. The system of claim12, wherein the electronic current driver circuit output connectionpoints are comprised of an array with identical spacing to match thedevice spacing of the vertical cavity surface emitting lasers on thesubstrate chip containing the linear laser array.
 17. The system ofclaim 12, wherein the semiconductor lasers are vertical cavity surfaceemitting lasers configured in an array.
 18. The system of claim 12,further comprising a computer which generates the digital data streamfrom external input including, but not limited to, the digital file ofthe image to be printed, the speed at which the print media is movingthrough at least one of the system, a physical location of each laser inthe system, a performance characteristics of each laser in the system.19. A system for electronically controlling and driving a plurality ofindependently addressable semiconductor lasers, comprising: verticalcavity surface emitting lasers arranged in a linear array comprised ofat least 100 laser devices on a common substrate chip and a dedicatedchannel associated with an address trace line and connection point foreach of the vertical cavity surface emitting lasers, wherein thevertical cavity surface emitting lasers are configured in the lineararray to generate a linear image resolution of at least 300 dpi; anelectronic current driver circuit that individually controls the lightoutput of each vertical cavity surface emitting laser by providingelectric drive current to the each vertical cavity surface emittinglaser through the connection point and address trace line associatedwith the each vertical cavity surface emitting laser, wherein thevertical cavity surface emitting lasers are configured to produce alinear image on a surface; a control interface circuit, wherein thecontrol interface circuit receives a stream of digital image data from acomputer and converts the digital image data into raw data which theelectronic current driver circuit uses to apply current to the eachvertical cavity surface emitting laser at an appropriate time, whereinthe control interface circuit and the electronic current driver circuitare implemented on an ASIC, and wherein the control interface circuitand the electronic current driver circuit are paired with a substratechip containing the linear array; and an interposer chip thatcommunicates with the ASIC and the substrate chip containing the linearlaser array, wherein the interposer has an array of input electricalconnection points and an array of output electrical connection points,wherein each input connection point is electrically connected to exactlyone output connection point, wherein the array of input connectionpoints is in close proximity to the ASIC and the spacing betweeninterposer input connection points is identical to the spacing of theASIC output connection points for the laser current driver circuit, andwherein the array of output connection points on the interposer chip isin close proximity to the substrate chip containing the linear array andthe spacing between interposer output connection points is identical tothe spacing of the device connection points on the substrate chipcontaining the linear array.
 20. The system of claim 19, furthercomprising a computer which generates the stream of digital image datafrom external input including a digital file of the image to be printed,the speed at which the print media is moving through at least one of thesystem, a physical location of the each vertical cavity surface emittinglaser in the system, a performance characteristics of each laser in thesystem.